Our research program continues to focus on three broad areas. These encompass: I) Molecular Regulation of HIV-1; II) Molecular Regulation of HTLV-I; and III) Molecular applications relevant for the development of HIV-1 specific ribozymes and transdominant/attenuated human immunodeficiency viruses. Here I summarize our progress over the past year. A more detailed visualization of our research is reflected in our annual bibliography. In brief, our research in 1994-1995 are described with the following 11 points. Recent selected findings include: 1) progress in understanding the modulation of Sp1 phosphorylation by HIV-1 Tat; 2) the in vivo selection of Tat mutants through forced high passage of recombinant HIV-1 genomes containing insertion of a Tat cDNA into nef; 3) the demonstration of a physical interaction between HIV-1 Tat and cellular protein kinase, PKR; 4) the characterization of a cellular function for TAR-RNA-binding protein, TRBP; 5) the discovery of a physical interaction between secreted Tat protein and cellular growth factor, epithelin; 6) the development of chimeric HIV-1 and SIVmac nef- HSVtk+ viruses as possible viral vaccine strains; 7) the optimization of semliki forest virus as an anti-HIV-1 ribozyme vector; 8) the isolation and characterization of cDNAs that encode cellular proteins that bind to HTLV-I Tax using the yeast two hybrid system; 9) the definition of a novel repressive effect of HTLV-I Tax on the c-myc oncoprotein; 10) the subnuclear localization of the HTLV-I Tax protein using confocal microscopy; 11) the characterization of differences between HTLV-I and -II Tax proteins in the induction of micronuclei.